Acid mine drainage (AMD) is formed when water and air come in contact with pyrite (FeS2) present in coal and exposed rocks, to form sulphuric acid. The process of pyrite oxidation further leads to the formation of Fe3+ and some or all of this Fe3+ precipitates to cause red, orange or yellowish colour of the water. The coal deposits in Meghalaya, India along the southern fringe of Shillong plateau are distributed in Khasi, Garo and Jaintia hills .